Temperature-alarm.



W. T. MUNRO. TEMPERATURBALARM.

APPLICATION FILED SEPT. 22, 1904.

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PATENTED JULY 17, 1906.

UNITED STATES PATENT OFFICE.

TEMPERATURE-ALARM.

Specification of Letters Patent.

Patented July 17, 1906.

Applic i n l September 22,1904. Serial No. 225,464.

To a, whom it may concern;

Be it known that I, WILLIAM TOM MUNRO, analytical chemist, a subject of the King of Great Britain, residing at East Blairlinn, Oumbernauld, county of Stirling, Scotland, have invented certain new and useful Improvements in Temperature-Alarms, of which the following is a specification.

This invention relates to that class of temperature-alarms wherein the expansion of air or gas acting on a suitable substance, such as mercury, causes the latter to close an electric circuit and sound an alarm and (or) operate an indicator or automatically close fireproof doors, actuate sprinklers, or the like. The arrangement is such that an alarm is given both on a very gradual rise of temperature and. on a sudden rise of temperature.

Under my invention I so construct the apparatus that when there is a gradual rise of temperature the mercury or other substance gradually expands under the influence of heat and closes (or opens) the electric circuit, whereas when the rise of temperature is sudden a pressure is exerted on the mercury, so as to force it to close (or open) the circuit by the differential action caused by the expansion of air contained in two vessels whose walls are of different thicknesses. The closing (or opening) of the electric circuit sounds the alarm.

In order that my said invention may be properly understood, I have hereunto ap pended an explanatory sheet of drawings, whereon Figure 1 is a front view of one form of the automatic temperature-alarm, while Figs. 2 and 3 are slightly-modified arrangements of the alarm. In Figs. 2 and 3 the bulbs A B are not shown.

In carrying out my invention with special reference to Figs. 1 and 2 of the drawings I construct the temperature-alarm witn two bulbs A B, made of glass or other suitable material. The one bulb A has a thinner wall than the other bulb B, and both bulbs are connected together by means of a glass or other tube C, provided with a capillary passage-way the bore of which may be of rectan gular, square, or other suitable section. This tube O has formed in its length two small bulbs D E. Two electric terminal wires F G are also fitted in the tube C and are in communication with the'capillary passage-way.

The instrument is filled with mercury or other suitable substance from the top of the small bulb D to a point H in the horizontal (or nearly horizontal) part of the tube C. The top of the bulb D is at such a height above the horizontal part of the tube O that the weight of the column of mercury above said horizontal part compensates for the difference between the pressure in the bulbs A and B, due to the forcing of the air contained in the capillary tube C from the bottom of the small bulb E to the point H into the bulb B. The terminal wires F G are sealed in the capillary tube O. The one F may be in the vertical part of the tube below the bulb D, while the other, G, may be in the horizontal part of the tube and clear of the mercury column when the latter is in its normal position. Of course, if desired, both terminal wires may be in the horizontal part of the tube O, provided they are arranged so that the circuit can be completed when necessary by the expansion of the mercury column.

With this invention under a gradual rise of temperature the action is as follows: The heat acting gradually on the bulbs A B is practically conducted through the walls of both bulbs as rapidly as it reaches them, whereby the increase of pressure due to the expansion of the media in A and B is equalized, and no pronounced movement of the mercury takes place along the horizontal tube. If there is a continued rise of temperature, however, the mercury itself will expand and travel along the horizontal part of the tube C until it passes the terminal G, and thereby closes the electric circuit and gives an alarm. When the rise of temperature is sudden, the heat acts quickly on the instrument and is of course conducted more rapidly through the thin-walled bulb A than through the thicker-walled bulb B. As a result the medium in the bulb A expands before the heat reaches the medium in the bulb B and in its expansion displaces the mercury or other suitable substance in the small bulb D and causes the mercury to travel along the tube O past the point I-I until it meets the terminal G, when the electric circuit is closed (or opened) and the alarm given.

By the use of the small bulb D, formed on the vertical part of the tube C, an extended horizontal movement of the mercury in the tube O is more readily obtained when the apparatus is in operation, as a slight vertical depression of the mercury in the bulb D causes a considerable increase in the extent of the movement of the mercury in the hori- ICC ITO

zontal part of the tube C. With this arrangement of apparatus the instrument may be rendered very sensitive and extremely suitable for indicating small rires of temperature. The bulb D need not be smaller than the bulb E, as shown, but may be of a similar size, or, if desired, in cases where an extremely sensitive instrument is required the bulb D may be dispensed with altogether and the bulb E made sufficiently large to hold enough of mercury to reach the terminal G by expansion; but in this case the depression would have to be very slight, and therefore 1 find it more convenient to use two bulbs, or, if desired, the bulb D may be made sufficiently large and the bulb E dispensed with.

The bulb E, as illustrated, has two func tions to perform. First, it acts as a reservoir for the mercury necessary to prod uee the expansion at a given temperature and. close (or open) a circuit, and, secondly, it enables the instrument to be reset, should it get shaken up in transit, in thefollowin manner: The instrument is laid on its side and the thick bulb B heated until the expansion of the air or gas therein forces the mercury through and clear of the curved part of the capillary tube G into the bulbs E and A, the bulb E being about half full. Of couse if there were any mercury in the bulb B to start with the instrument would require to be held vertical when the heat was "first applied thereto until all the mercury was removed from the bulb B, when the operation of clearing the capillary tube C could be concluded by placing the instrument in a horizontal position. The instrument is then allowed to cool in a horizontal position, with the result that the or gas in. the bulbs A and B attains the same pressure. \Vhen cold, the instrument raised into the vertical position, and the mercury is thus caused to trap the air at the bottom of the bulb E. The bulb A is now heated, the mercury being thus forced down into the bulb E and the instrument allowed to cool. hen cool, the mercury in the instrument assumes the position shown in, dotted lines at Fig. 1 of the drawings. The air or at the bottom of the bulb E having been displaced from the bulb A and forced mto the bulb B by the above operations, it naturally follows that the air 'or gas in. the bulb B is at a greater pressure than that in the bulb A, this greater pressure being compensated for by the weight of the column of mercury from the top of the bulb D to the point H in the horizontal part of the capillary tube C. It has also been found that by varying the angle or slope of the horizontal part of the tube C the sensitiveness of the instrument may be varied, and in order that the instrument may be equally sensitive at all temperatures the horizontal part of the tube C may be made with a slight bend or inclination toward the thick bulb B. As the mercury in the instrument expands unde' a rise in temperature the end Tl of the mercury (see Fig. 1) gets nearer the terminal G, with the result that owing to such expansion the higher the temperature the less depression of the mercury in the bulb D is required to complete the contact and the more sensitive the instrument becomes, and. if the instrument is made with the horizontal part of the tube slightly inclined toward the bulb B it follows that as the mercury expands toward the terminal G the point ll is raised to a slightly-higherlevel, and a force corresponding to the weight of the mercury column between the new position of the point ll and the original position thereof is necessary before the mercury can be moved at all. Further, the mercury expands in the bulb D; but the resisting force of the capillary tube above the bulb D prevents the expanded mcrcury entering this tube, and it is therefore pressed against the end of the tube above the bulb with a pressure corresponding to the distance through which the point II has been moved by the expansion of the mercury in the tube C, and this resistance has to be overcome before the mercury moves. ()wing to the slope of the tube C and the compression of air in this tube between the points If and the tern'iinal G the resistz'mce is much greater the nearer the point ll. is to the terminal (i, and it compensates for the small depression of themercury in the bulb I) required to complete the circuit. ()n the other hand, when the instrument is cooled below the normal temperature the mercury in contracting comes down the inclined tube (1, and the point .l'l reaches a lower level; but as the mercury in the tube falls the mercury at the top of the bulb D must also fall, and as the surface of the mercury in the bulb 1) falls it l)6C()IT1(.S larger, and a slightcr depression is therefore necessary to complete the circuit. ()wing to the large contraction of the mercury necessary to produce even a slight lowering of the surface of the mercury in the bulb D a very great lowering of temperature is necessary to move the point ll. down the sloped tube even a small distance, and by this means the instrument is made practically equally sensitive for all temperatures. For general purposes, however, it will be found desirable to have alarms as constructed under my invention more sensitive at higher ten'iperatures, and therefore it will not be necessary to make them with the horizontal part of the tube slightly inclined upward, as above described. The slight upward bend or inclination in the tube U being dispensed with, the compres sion of the medium in the bulb B alone will be used for the manipulation of the degree of scnsitiveness. in certain Classes of apparatus, however, where it may be found desirattached to the horizontal part of the tube given.

C. When the pointer J is moved to one or other of the divisions marked on the dial K, the instrument is caused to assume a new po sition say that indicated in dotted lines in the figure. With this arrangement the slope required for any degree of sensitiveness is readily given to the horizontal part of the tube U. The slope may either be upward or downward.

The construction of apparatus illustrated at Fig. 3 is similar to that shown at Figs. 1 and 2; but the terminals F G are fitted in such a position that they are permanently covered by the mercury, so that a continuous current flows through the electric circuit. With this arrangement when a sudden rise of temperature takes place the media in the bulbs A B (not shown) act as before, and the mercury is forced along the tube C until it reaches a small cup L, into which it flows, at the same time drawing away the mercury from the terminal F, so that the electric circuit is broken at that point and an alarm WVhen the temperature rises gradually, the mercury expands until it reaches the small cup L, when it is siphoned over into same, thereby drawing away the mercury from the terminal F and breaking the circuit, as before, so as to give an alarm.

If desired, the apparatus may be made to act very suddenly either by increasing the diameter of the bulb D or by bringing the end of the mercury in the horizontal part of the tube C nearer to the terminal G.

When the apparatus is used on board ship, it is preferably mounted on trunnions, gimbals, or the like to insure that it will always remain steady and in the proper vertical or nearly vertical working position.

Should it be desired to give an alarm when the instrument is broken, a third terminal, as indicated in dotted lines at M, Fig. 3, would be used. This terminal would be fitted in the tube C somewhere between the terminals F and G. The media in the bulbs A B may be either at a greater or less pressure than the atmosphere, and the action would be the same as that of the continuous-current apparatus already described. When the media in the instrument is at a greater pressure than the atmosphere under a gradual or sudden rise, the contact is broken at the terminal F, and then the current flows through the two terminals G M and indicates accordingly. The instrument is so arranged that it is practically impossible (say during a fire) for the pressure in the bulb A to become so much greater than the pressure in the bulb B as to On force the mercury from the terminal M. the other hand, should the instrument be broken, say, at the bulb A the difierence in pressure between the media of the instrument and the atmosphere causes the media in that part of the instrument still trapped by the mercury to expand and break the contact by driving the mercury oil the terminal G, and the current flowing freely through the two terminals M and F would cause the instrument to partially indicate until the mercury was driven oil the terminal M when the cir cuit would be completely broken, and the current could not How through the instrument at all. If the instrument were broken at the bulb B, the current would first be broken at the terminal F; but it would continue to flow through the terminals M and G until the terminal M was uncovered, when it would stop flowing. Should the instrument be broken at the terminal M, then the current would not flow through the instrument at all.

When the media in the instrument is at less pressure than the atmosphere and the bulb A is broken, the current would first be broken at the terminal F and then at the ter minal M. If the instrument be broken at the bulb B, the current would first be broken at the terminal G and then at the terminal M.

With this construction of apparatus the bulbs A B may be made of equal or unequal sizes and, if desired, of any other convenient material than glass.

Having now fully described my invention, what I claim, and desire to secure by Letters Patent, is

1. An automatic temperature-alarm comprising in combination, two bulbs the wall of the one bulb being thicker than that of the other, a capillary tube having mercury there in, connecting the two bulbs, two smaller bulbs in the capillary tube and electric terminals in said tube, substantially as described.

2. An automatic temperature-alarm comprising in combination two bulbs containing air or gas, a capillary tube having mercury therein, said tube extending down vertically from the one bulb and then bending round until horizontal and thereafter bending up vertically to the other bulb, two smaller bulbs arranged in the vertical part of the capillary tube and electric terminals in said tube.

3. An automatic temperature-alarm comprising in combination, two bulbs for air or gas, a tube connecting these bulbs and hav ing mercury therein, electrical terminals in the tube and means for rotating the alarm substantially as described.

4. An automatic temperature-alarm comprising in combination, two bulbs for air or gas, a tube connecting these bulbs and having mercury therein, electrical terminals in the tube, a pivot for the tube and an indicator, substantially as described.

5. An automatic temperature-alarm comprising in combination, two bulbs the wall of the one bulb being thicker than that of the other, a capillary tube having mercury therein connecting the two bulbs, three smaller bulbs in the capillary tube and electric terminals in said tube, substantially as described.

6. An automatic temperature-a1arm comprising in combination two bulbs containing air or gas, a capillary tube having mercury i therein, said tube extending down vertically from the one bulb and then bending round in a curve until horizontal and thereafter bend ing up vertically to the other-bulb, two smaller bulbs arranged in the vertical part of the capillary tube and electric terminals in said tube.-

Signed at Glasgow, 01 September, 190% l/VILLI AM TOM MUNRO. Witnesses:

\VILLIAM GALL, VVILLlAhl, FLEMING.

Scotland, this 5th day i 

